The present disclosure relates to a drive control device operable to drive and control a panel module for display and touch detection and a piece of electronic equipment arranged by mounting the drive control device on a panel module, and further relates to a technique useful in application for the increase in display quality in a portable information terminal device, e.g. a tablet or a smart phone.
A portable information terminal device, such as a tablet or a smart phone, has a panel module disposed on a surface; the panel module is arranged by putting together or integrally forming a display panel and a touch panel. Such a portable information terminal device is able to determine, from touch coordinates, a touch operation performed on a surface of the touch panel by a finger or the like according to screen display on the display panel in the event of the touch operation. In these days, electrostatic capacitance type touch panels have been in wide use; an electrostatic capacitance type touch panel is arranged to make discrimination between a touch and no touch based on the change or difference in detection signal according to the value of a stray capacitance on detection electrodes arranged like an array.
A liquid crystal panel has scan electrodes and signal electrodes, which are arranged to cross each other, and thin film transistors disposed at their intersecting points; the thin film transistors are each referred to as “TFT”. The thin film transistors are arranged in such a way that the gate of each transistor is connected to the corresponding scan electrode, the source is connected to the corresponding signal electrode, and a liquid crystal element and a storage capacitor which make a sub-pixel are connected between the drain and a common electrode, whereby respective pixels are formed. In display control, the scan electrodes are activated sequentially. Thus, the thin film transistors are turned ON for each scan electrode and an electric current is caused to flow between the source and drain, during which signal voltages put on the source electrode lines are applied to the respective liquid crystal elements, consequently bringing them into a transmission state.
With a display panel and a touch panel put together or integrally formed, a capacitive coupling is caused between the display panel and the touch panel. Using high drive pulse voltages for driving the detection electrodes of the touch panel, the noise causes an adverse effect on the display panel through the capacitive coupling.
In addition, the influence of the noise attributed to the capacitive coupling, etc. between the display panel and the touch panel which are superposed on each other or integrally formed reaches even the display panel to the touch panel. Activating the touch panel to perform a touch detection during a non-display drive term rather than a display drive term of the display panel in a cycle of a frame synchronizing signal of a display frame (also, hereinafter referred to as “frame” simply), the noise owing to a drive display action of the display panel, and the noise of a detection action of the touch panel can be prevented from affecting each other. Especially, in a case where the relation between the display and the non-display drive terms is fixed in a cycle of the frame synchronizing signal, the difference in brightness arises in a display frame at each boundary of display and non-display drive terms; the larger the number of times the display and non-display drive terms are repeated is, the more remarkable the degradation of display quality owing to the undesired brightness difference is. Further, the aging arises in display elements of the display line covering each boundary of the display and non-display drive terms, which leads to the change in light transmittance and appears to make a horizontal stripe in a display screen in e.g. an LC (liquid crystal) display device.
Such being the case, a display controller arranged so that the start timings of display and non-display drive terms in the cycle of the frame synchronizing signal of a display frame can be changed at intervals of one or a plurality of cycles of the frame synchronizing signal is adopted in the Japanese Unexamined Patent Application Publication No. JP-A-2014-146093, which controls a display panel so that the display action is performed in a display drive term and the touch detection action is conducted in a non-display drive term. According to this, the boundary of display and non-display drive terms is not fixed, and such boundaries are distributed over a whole display screen, whereby the display quality can be prevented from being degraded by the undesired brightness difference resulting from the iteration of display and non-display drive terms and further, the degradation of display quality owing to local degradation as a result of the aging at the boundaries distributed over the whole display screen can be prevented.